The present invention relates to a control method of transmitting power in a cellular system with a transmitting side and a receiving side. The method compares a signal to interference power ratio (SIR) of a received signal at the receiving side with a target SIR, and then controls the transmitting power at the transmitting side depending upon the comparison result such as its difference and higher or lower.
In general, a bidirectional radio link is connected between a base station and a mobile station in a cellular system. In a CDMA (Code Division Multiple Access) cellular system using a CDMA link which is one of radio links between the mobile station and the base station, all the mobile stations transmit uplink signals at the same frequency. Also, all the base stations transmit downlink signals at the same frequency. The frequency of the uplink signals differs from that of the downlink signals, and therefore FDD (Frequency Division Duplex) method is used.
Since the same frequency is used in the uplink or downlink transmission, transmitted signals from one mobile station or one base station will interfere with a signal from another mobile station or base station. The higher the transmitted power, the larger the interference of the transmitted signal. Thus, in the CDMA cellular system, both the mobile stations and the base stations control the transmitting power of them to hold down the transmitted power to necessary minimum and reducing the interference. In general, the transmitting power control at the mobile station is called as an uplink transmitting power control, and the transmitting power control at the base station is called as a downlink transmitting power control.
When performing the transmitting power control at the mobile station, the base station measures a received SIR of a received signal from this mobile station and compares the measured received SIR with a target SIR. If the received SIR is higher than the target SIR, the base station instructs the mobile station to reduce the transmitting power. If the received SIR is lower than the target SIR, the base station instructs the mobile station to increase the transmitting power.
The transmitting power control at the base station is similarly performed as the transmitting power control at the mobile station except that the mobile station and the base station change places.
According to the above-mentioned transmitting power control, the received SIR is substantially kept at constant. However, even if the received SIR is constant, a communication quality factor such as a frame error rate (FER) or a bit error rate is not always kept constant.
In order to keep the FER or the bit error rate at constant, an outer loop control method may be used. According to this outer loop control method, a target SIR is increased if a communication quality factor such as a FER or a bit error rate detected at the receiving side is worse than a desired quality factor, and the target SIR is reduced if the detected communication quality factor is better than the desired quality factor.
A first conventional outer loop control method is described for example in Usuda et al., xe2x80x9cEffects of applying outer loop transmit power control to W-CDMA Systemxe2x80x9d, 1998 IEICE (Institute of Electronics, Information and Communication Engineers) General Conference, B-5-114, March 1998. In this method, a FER is measured by exponent weighting, the measured FER is compared with a target FER at every fixed number of frames and then a target SIR corresponding to the target Eb/Io described in the literature is increased or decreased by a predetermined value (the same value in increasing and in decreasing) depending upon the result of the comparison. A modified method of this is described in Higuchi et al., xe2x80x9cExperimental performance of adaptive transmit power control using outer loop for wideband-CDMAxe2x80x9d, 1998 IEICE General Conference, B-5-92, March 1998. In the latter modified method, a FER is measured by counting the number of frame errors for every fixed number of frames.
In a second conventional outer loop control method, whether or not a frame error exists is detected for every frame. When there is a frame error, a constant value S1 makes a target SIR increase, and when there is no frame error, a constant value S2 decreases the target SIR. If the target FER is expressed by p, the long average FER will become equal to the target FER by determining S1 and S2 to satisfy the following equation;
S1xc3x97p=S2xc3x97(1xe2x88x92p).
First Problem
However, according to the first conventional outer loop control method, if the FER measurement time is short, the target SIR will be decreased because the measured FER may often zero when the probability of FER is substantially equal to the target FER. Namely, when the outer loop control becomes a steady state, the actual FER probability is higher than the target FER. In other words, according to the first conventional outer loop control method, a long measurement time equal to or longer than 1/p with respect to the target FER (=p) is necessarily required and therefore the required measurement time becomes extremely long when the target FER is low. Thus, the control may not quickly respond to change in the required SIR when it fast varies due to for example rapid change of environment.
Whereas, according to the second conventional outer loop control method, the difference between the increment amount of SIR S1 and the decrement amount of SIR S2 becomes large when the target FER is low. If the SIR increment amount S1 is increased, excess increasing of the target SIR will occur due to probable frame error generations under the conditions that the required SIR does not change, causing the average SIR to increase. This results that the average transmitting power at the transmitting side becomes higher than required. Contrary to this, if the SIR increment amount S1 is decreased, the SIR decrement amount S2 is decreased in proportional to it. Thus, the control may not quickly respond to change in the required SIR when it fast decreases due to for example rapid change of environment.
Second Problem
There may be a lower limit in the transmitting power due to for example functional restrictions of a unit. Thus, a state that the received SIR at the receiving side exceeds the target SIR and there is no frame error although the transmitting power has its lower limit may be happened. At such state, if the outer loop control is being executed, the target SIR will decrease without limits. After that, if the state changes into one with frame errors, since the target SIR was decreased to quite lower value than its correct required SIR, frame errors will occur at higher probability than the target FER until the target SIR comes back to its correct value by the above-mentioned outer loop control.
Third Problem
When control of changing on/off of transmission for every frame is performed at the transmitting side as in the DTX (Discontinuous Transmission) control, the receiving side may erroneously judge that a frame error is occurred at the off-transmission frame. In this case, if the above-mentioned outer loop control is executed, the FER is measured higher than the actual FER and thus the target SIR will become higher than required.
Fourth Problem
In CDMA cellular system, in general, handover operations such as soft handover operation and softer handover operation are adopted. At each of the handovers, a plurality of radio links are simultaneously connected. However, the required SIR who is necessary to obtain the target FER may vary depending on the number of the connected links and kinds of the handovers. In such case, if the above-mentioned outer loop control is carried out, response will be delayed due to change in the number of the connected links and kinds of the handovers causing many frame errors to occur and also causing the target SIR to increase higher than required.
It is therefore an object of the present invention to provide a control method of transmitting power in a cellular system, whereby at least one of the aforementioned first to fourth problems can be solved.
According to the present invention, a control method of transmitting power in a cellular system includes a step of measuring a SIR of a received signal at the receiving side, a step of detecting frame errors of the received signal at the receiving side, a step of counting the number of the detected frame errors n(k) (k and n(k) are positive integers and 1xe2x89xa6kxe2x89xa6xe2x89xa6K) for every M(k) (M(k) is a positive integer) frames, or for last N(k) (N(k) is a positive integer) frames just before the frame error is detected, a step of adjusting a value of a target SIR depending on one or set of the counted numbers of frame error n(1) to n(K), a step of comparing the measured SIR with the adjusted target SIR to provide a compared result, and a step of controlling at the transmitting side the transmitting power depending on the compared result.
Since the spacing (M(k) frames) of the control for adjusting a target SIR can be set up independently of the number of frames (N(k) frames) equivalent to the period for counting the number of frame errors, the degree of freedom at the time of carrying out the present invention can increase. Namely, if M(k) is set up smaller than N(k), the delay time from a frame error occurrence to the adjustment of the SIR can be made small. Thus, it is possible to respond to rapid change of the required SIR. Also, by setting up only M(k) greatly, the throughput for performing a present invention can be reduced.
It is preferred that wherein, in case of K=1, the adjusting step includes comparing the counted number of frame error n(1) with thresholds t1 and t2 (t1xe2x89xa7t2), increasing the value of the target SIR by a value S1 when n(1)xe2x89xa7t1, and decreasing the value of the target SIR by a value S2 when n(1)xe2x89xa6t2.
It is also preferred that, in case that there is a difference xcex94SIR between the target SIR and a required SIR which satisfies a target FER, the adjusting step further includes setting the values S1 and S2 to satisfy equation of
S1xc3x97P1xe2x88x92S2xc3x97P2=xcex94SIR
where P1 is a probability of that relationship of the number of frame errors n(1) with respect to the threshold t1 becomes n(1)xe2x89xa7t1, and P2 is a probability of that relationship of the number of frame errors n(1) with respect to the threshold t2 becomes n(1)xe2x89xa6t2.
It is preferred that, in case that there is a difference xcex94SIR between the target SIR and a required SIR which satisfies a target FER, the adjusting step further includes setting the values S1 and S2 to satisfy equation of
10{circumflex over ( )}(S1/10)xc3x97P1+10{circumflex over ( )}(xe2x88x92S2/10)xc3x97P2+(1xe2x88x92P1xe2x88x92P2)=10{circumflex over ( )}(xcex94SIR/10)
where P1 is a probability of that relationship of the number of frame errors n(1) with respect to the threshold t1 becomes n(1)xe2x89xa7t1, and P2 is a probability of that relationship of the number of frame errors n(1) with respect to the threshold t2 becomes n(1)xe2x89xa6t2.
The difference xcex94SIR may be set to a value equal to or higher than xe2x88x922 dB and lower than 0 dB, or a value equal to or lower than 2 dB and higher than 0 dB.
It is preferred that the adjusting step further includes setting the values S1 and S2 to satisfy equation of
S1xc3x97P1=S2xc3x97P2
where P1 is a probability of that relationship of the number of frame errors n(1) with respect to the threshold t1 becomes n(1)xe2x89xa7t1 when a FER is equal to the target FER, and P2 is a probability of that relationship of the number of frame errors n(1) with respect to the threshold t2 becomes n(1)xe2x89xa6t2 when the FER is equal to the target FER.
It is also preferred that the adjusting step further includes setting the values S1 and S2 to satisfy equation of
10{circumflex over ( )}(S1/10)xc3x97P1+10{circumflex over ( )}(xe2x88x92S2/10)xc3x97P2=P1+P2
where P1 is a probability of that relationship of the number of frame errors n(1) with respect to the threshold t1 becomes n(1)xe2x89xa7t1 when a FER is equal to the target FER, and P2 is a probability of that relationship of the number of frame errors n(1) with respect to the threshold t2 becomes n(1)xe2x89xa6t2 when the FER is equal to the target FER.
It is preferred that the method further has preparing a table for storing increase and decrease values of target SIR corresponding to the number of frame errors n(1), and that, in case of K=1, the adjusting step includes obtaining an increase or decrease value from the table depending on a newest number of frame error n(1) when it is updated, and increasing or decreasing the value of the target SIR by the obtained value.
It is preferred that, in case that there is a difference xcex94SIR between the target SIR and a required SIR which satisfies a target FER, the increase and decrease values of target SIR stored in the table are set to satisfy equation of             ∑              i        =        0            N        ⁢                  S        ⁢                  (          i          )                    xc3x97              P        ⁢                  (          i          )                      =      Δ    ⁢          xe2x80x83        ⁢    SIR  
where P(i) is a probability of that the number of frame errors n(1) becomes equal to i (0xe2x89xa6ixe2x89xa6N=N(1)), and S(i) is the increase and decrease value of the target SIR when the of frame errors n(1) is equal to i (0xe2x89xa6ixe2x89xa6N=N(1)) and when increasing and decreasing are indicated by positive and negative polarities.
It is also preferred that, in case that there is a difference xcex94SIR between the target SIR and a required SIR which satisfies a target FER, the increase and decrease values of target SIR stored in the table are set to satisfy equation of             ∑              i        =        0            N        ⁢                  10        ^                  (                                    S              ⁢                              (                i                )                                      /            10                    )                    xc3x97              P        ⁢                  (          i          )                      =      10    ^          (              Δ        ⁢                  xe2x80x83                ⁢                  SIR          /          10                    )      
where P(i) is a probability of that the number of frame errors n(1) becomes equal to i (0xe2x89xa6ixe2x89xa6N=N(1)), and S(i) is the increase and decrease value of the target SIR when the of frame errors n(1) is equal to i (0xe2x89xa6ixe2x89xa6N=N(1)) and when increasing and decreasing are indicated by positive and negative polarities.
The difference xcex94SIR may be set to a value equal to or higher than xe2x88x922 dB and lower than 0 dB, or a value equal to or lower than 2 dB and higher than 0 dB.
It is preferred that the increase and decrease values of target SIR stored in the table are set to satisfy equation of             ∑              i        =        0            N        ⁢                  S        ⁢                  (          i          )                    ⁢              P        ⁢                  (          i          )                      =  0
where P(i) is a probability of that the number of frame errors n(1) becomes equal to i (0xe2x89xa6ixe2x89xa6N=N(1)) when a FER is equal to the target FER, and S(i) is the increase and decrease value of the target SIR when the of frame errors n(1) is equal to i (0xe2x89xa6ixe2x89xa6N=N(1)) and when increasing and decreasing are indicated by positive and negative polarities.
It is also preferred that the increase and decrease values of target SIR stored in the table are set to satisfy equation of             ∑              i        =        0            N        ⁢                  10        ^                  (                                    S              ⁢                              (                i                )                                      /            10                    )                    xc3x97              P        ⁢                  (          i          )                      =  1
where P(i) is a probability of that the number of frame errors n(1) becomes equal to i (0xe2x89xa6ixe2x89xa6N=N(1)) when a FER is equal to the target FER, and S(i) is the increase and decrease value of the target SIR when the of frame errors n(1) is equal to i (0xe2x89xa6ixe2x89xa6N=N(1)) and when increasing and decreasing are indicated by positive and negative polarities.
The number of frames N(1) may be equal to the number of frames M(1).
Preferably, the adjusting step is stopped from doing during N(1) frames just after the target SIR is once adjusted.
It is preferred that, in case of K=2, the adjusting step includes comparing the counted numbers of frame error n(1) and n(2) with thresholds t1 and t2 (t1xe2x89xa7t2), increasing the value of the target SIR by a value S1 when n(1)xe2x89xa7t1, and decreasing the value of the target SIR by a value S2 when n(2)xe2x89xa6t2.
It is more preferred that, in case that there is a difference xcex94SIR between the target SIR and a required SIR which satisfies a target FER, the adjusting step further includes setting the values S1 and S2 to satisfy equation of
S1xc3x97P1xe2x88x92S2xc3x97P2=xcex94SIR
where P1 is a probability of that relationship of the number of frame errors n(1) with respect to the threshold t1 becomes nxe2x89xa7t1, and P2 is a probability of that relationship of the number of frame errors n(2) with respect to the threshold t2 becomes n(2)xe2x89xa6t2.
It is also preferred that, in case that there is a difference xcex94SIR between the target SIR and a required SIR which satisfies a target FER, the adjusting step further includes setting the values S1 and S2 to satisfy equation of
10{circumflex over ( )}(S1/10)xc3x97P1+10{circumflex over ( )}(xe2x88x92S2/10)xc3x97P2+(1xe2x88x92P1xe2x88x92P2)=10{circumflex over ( )}(xcex94SIR/10)
where P1 is a probability of that relationship of the number of frame errors n(1) with respect to the threshold t1 becomes n(1)xe2x89xa7t1, and P2 is a probability of that relationship of the number of frame errors n(2) with respect to the threshold t2 becomes n(2)xe2x89xa6t2.
The difference xcex94SIR may be set to a value equal to or higher than xe2x88x922 dB and lower than 0 dB, or a value equal to or lower than 2 dB and higher than 0 dB.
It is preferred that the adjusting step further includes setting the values S1 and S2 to satisfy equation of
S1xc3x97P1=S2xc3x97P2
where P1 is a probability of that relationship of the number of frame errors n(1) with respect to the threshold t1 becomes n(1)xe2x89xa7t1 when a FER is equal to the target FER, and P2 is a probability of that relationship of the number of frame errors n(2) with respect to the threshold t2 becomes n(2)xe2x89xa6t2 when the FER is equal to the target FER.
It is also preferred that the adjusting step further includes setting the values S1 and S2 to satisfy equation of
10{circumflex over ( )}(S1/10)xc3x97P1+10{circumflex over ( )}(xe2x88x92S2/10)xc3x97P2=P1+P2
where P1 is a probability of that relationship of the number of frame errors n(1) with respect to the threshold t1 becomes n(1)xe2x89xa7t1 when a FER is equal to the target FER, and P2 is a probability of that relationship of the number of frame errors n(2) with respect to the threshold t2 becomes n(2)xe2x89xa6t2 when the FER is equal to the target FER.
Preferably, the adjusting step is stopped from doing during N(1) frames just after the target SIR is once increased and during N(2) frames just after the target SIR is once decreased.
It is preferred that the method further includes preparing a table for storing increase and decrease values of target SIR corresponding to a set of the numbers of frame errors (n(1), n(2), . . . , n(K)), and that the adjusting step includes obtaining an increase or decrease value from the table depending on a newest set of the numbers of frame error (n(1), n(2), . . . , n(K)) when one of the numbers of frame errors n(1), n(2), . . . , n(K) is updated, and increasing or decreasing the value of the target SIR by the obtained value.
It is more preferred that, in case that there is a difference xcex94SIR between the target SIR and a required SIR which satisfies a target FER, the increase and decrease values of target SIR stored in the table are set to satisfy equation of             ∑                        i          ⁢                      (            1            )                          =        0                    N        ⁢                  (          1          )                      ⁢                  ∑                              i            ⁢                          (              2              )                                =          0                          N          ⁢                      (            2            )                              ⁢              …        ⁢                              ∑                                          i                ⁢                                  (                  K                  )                                            =              0                                      N              ⁢                              (                K                )                                              ⁢                                    S              ⁢                              (                                                      i                    ⁢                                          (                      1                      )                                                        ,                                      i                    ⁢                                          (                      2                      )                                                        ,                  …                  ⁢                                      xe2x80x83                                    ,                                      i                    ⁢                                          (                      K                      )                                                                      )                                      xc3x97                          P              ⁢                              (                                                      i                    ⁢                                          (                      1                      )                                                        ,                                      i                    ⁢                                          (                      2                      )                                                        ,                  …                  ⁢                                      xe2x80x83                                    ,                                      i                    ⁢                                          (                      K                      )                                                                      )                                                          =      Δ    ⁢          xe2x80x83        ⁢    SIR  
where P(i(1), i(2), . . . , i(K)) (0xe2x89xa6i(k)xe2x89xa6N(k), 1xe2x89xa6kxe2x89xa6K) is a probability of that the set of the numbers of frame errors (n(1), n(2), . . . , n(K)) becomes equal to (i(1), i(2), . . . , i(K)), and S(i(1), i(2), . . . , i(K)) is the increase and decrease value of target SIR when the set of the numbers of frame errors (n(1), n(2), . . . , n(K)) is equal to (i(1), i(2), . . . , i(K)) and when increasing and decreasing are indicated by positive and negative polarities, respectively.
It is also preferred that, in case that there is a difference xcex94SIR between the target SIR and a required SIR which satisfies a target FER, the increase and decrease values of target SIR stored in the table are set to satisfy equation of             ∑                        i          ⁢                      (            1            )                          =        0                    N        ⁢                  (          1          )                      ⁢                  ∑                              i            ⁢                          (              2              )                                =          0                          N          ⁢                      (            2            )                              ⁢              …        ⁢                              ∑                                          i                ⁢                                  (                  K                  )                                            =              0                                      N              ⁢                              (                K                )                                              ⁢                                    10              ^                              (                                                      S                    ⁢                                          (                                                                        i                          ⁢                                                      (                            1                            )                                                                          ,                                                  i                          ⁢                                                      (                            2                            )                                                                          ,                        …                        ⁢                                                  xe2x80x83                                                ,                                                  i                          ⁢                                                      (                            K                            )                                                                                              )                                                        /                  10                                )                                      xc3x97                          P              ⁢                              (                                                      i                    ⁢                                          (                      1                      )                                                        ,                                      i                    ⁢                                          (                      2                      )                                                        ,                  …                  ⁢                                      xe2x80x83                                    ,                                      i                    ⁢                                          (                      K                      )                                                                      )                                                          =      10    ^          (              Δ        ⁢                  xe2x80x83                ⁢                  SIR          /          10                    )      
where P(i(1), i(2), . . . , i(K)) (0xe2x89xa6i(k)xe2x89xa6N(k), 1xe2x89xa6k xe2x89xa6K) is a probability of that the set of the numbers of frame errors (n(1), n(2), . . . , n(K)) becomes equal to (i(1), i(2), . . . , i(K)), and S(i(1), i(2), . . . , i(K)) is the increase and decrease value of target SIR when the set of the numbers of frame errors (n(1), n(2), . . . , n(K)) is equal to (i(1), i(2), . . . , i(K)) and when increasing and decreasing are indicated by positive and negative polarities, respectively.
The difference xcex94SIR may be set to a value equal to or higher than xe2x88x922 dB and lower than 0 dB, or a value equal to or lower than 2 dB and higher than 0 dB.
It is preferred that the increase and decrease values of target SIR stored in the table are set to satisfy equation of             ∑                        i          ⁢                      (            1            )                          =        0                    N        ⁢                  (          1          )                      ⁢                  ∑                              i            ⁢                          (              2              )                                =          0                          N          ⁢                      (            2            )                              ⁢              …        ⁢                              ∑                                          i                ⁢                                  (                  K                  )                                            =              0                                      N              ⁢                              (                K                )                                              ⁢                      S            ⁢                          (                                                i                  ⁢                                      (                    1                    )                                                  ,                                  i                  ⁡                                      (                    2                    )                                                  ,                …                ⁢                                  xe2x80x83                                ,                                  i                  ⁢                                      (                    K                    )                                                              )                        ⁢                          P              ⁡                              (                                                      i                    ⁢                                          (                      1                      )                                                        ,                                      i                    ⁡                                          (                      2                      )                                                        ,                  …                  ⁢                                      xe2x80x83                                    ,                                      i                    ⁢                                          (                      K                      )                                                                      )                                                          =  0
where P(i(1), i(2), . . . , i(K)) (0xe2x89xa6i(k)xe2x89xa6N(k), 1xe2x89xa6kxe2x89xa6K) is a probability of that the set of the numbers of frame errors (n(1), n(2), . . . , n(K)) becomes equal to (i(1), i(2), . . . , i(K)) when a FER is equal to the target FER, and S(i(1), i(2), . . . , i(K)) is the increase and decrease value of target SIR when the set of the numbers of frame errors (n(1), n(2), . . . , n(K)) is equal to (i(1), i(2), . . . , i(K)) and when increasing and decreasing are indicated by positive and negative polarities, respectively.
It is also preferred that the increase and decrease values of target SIR stored in the table are set to satisfy equation of       ∑                  i        ⁢                  (          1          )                    =      0              N      ⁢              (        1        )              ⁢            ∑                        i          ⁢                      (            2            )                          =        0                    N        ⁡                  (          2          )                      ⁢          …      ⁢                        ∑                                    i              ⁢                              (                K                )                                      =            0                                N            ⁢                          (              K              )                                      ⁢                              10            ^                          (                                                S                  ⁡                                      (                                                                  i                        ⁢                                                  (                          1                          )                                                                    ,                                              i                        ⁡                                                  (                          2                          )                                                                    ,                      …                      ⁢                                              xe2x80x83                                            ,                                              i                        ⁡                                                  (                          K                          )                                                                                      )                                                  /                10                            )                                ⁢                      xc3x97                    ⁢                      P            ⁡                          (                                                i                  ⁢                                      (                    1                    )                                                  ,                                  i                  ⁡                                      (                    2                    )                                                  ,                …                ⁢                                  xe2x80x83                                ,                                  i                  ⁡                                      (                    K                    )                                                              )                                ⁢                      =                    ⁢          1                    
where P(i(1), i(2), . . . , i(K)) (0xe2x89xa6i(k)xe2x89xa6N(k), 1xe2x89xa6kxe2x89xa6K) is a probability of that the set of the numbers of frame errors (n(1), n(2), . . . , n(K)) becomes equal to (i(1), i(2), . . . , i(K)) when a FER is equal to the target FER, and S(i(1), i(2), . . . , i(K)) is the increase and decrease value of target SIR when the set of the numbers of frame errors (n(1), n(2), . . . , n(K)) is equal to (i(1), i(2), . . . , i(K)) and when increasing and decreasing are indicated by positive and negative polarities, respectively.
Preferably, the adjusting step is stopped from doing during frames just after the target SIR is once adjusted.
It is preferred that the method further includes preparing a table for storing increase and decrease values of target SIR corresponding to the numbers of frame errors n(1), n(2), . . . , n(K), respectively, and that the adjusting step includes obtaining an increase or decrease value from the table depending on a newest one n(k) of the numbers of frame error n(1), n(2), . . . , n(K) when the number of frame errors n(k) is updated, and increasing or decreasing the value of the target SIR by the obtained value.
It is also preferred that, in case that there is a difference xcex94SIR between the target SIR and a required SIR which satisfies a target FER, the increase and decrease values of target SIR stored in the table are set to satisfy equation of             ∑              k        =        0            K        ⁢                  ∑                              i            ⁢                          (              k              )                                =          0                          N          ⁢                      (            k            )                              ⁢                        1                      M            ⁢                          (              k              )                                      ⁢                  S          ⁢                      (                          k              ,                              i                ⁢                                  (                  k                  )                                                      )                          xc3x97                  P          ⁢                      (                          k              ,                              i                ⁢                                  (                  k                  )                                                      )                                =      Δ    ⁢          xe2x80x83        ⁢    SIR  
where P(k, i(k)) is a probability of that the number of frame errors during N(k) frames n(k) becomes equal to i(k) (0xe2x89xa6i(k)xe2x89xa6N(k)), and S(k, i(K)) is the increase and decrease value of target SIR when the number of frame errors n(k) is equal to i(k) and when increasing and decreasing are indicated by positive and negative polarities, respectively.
It is preferred that, in case that there is a difference xcex94SIR between the target SIR and a required SIR which satisfies a target FER, the increase and decrease values of target SIR stored in the table are set to satisfy equation of                               ∑                      k            =            0                    K                ⁢                              ∑                                          i                ⁡                                  (                  k                  )                                            =              0                                      N              ⁡                              (                k                )                                              ⁢                                    1                              M                ⁡                                  (                  k                  )                                                      ⁢                          10              ^                              S                ⁡                                  (                                      k                    ,                                                                  i                        ⁡                                                  (                          k                          )                                                                    /                      10                                                        )                                                                        )        xc3x97    P    ⁢          (              k        ,                  i          ⁡                      (            k            )                              )        =      10    ^          (              Δ        ⁢                  xe2x80x83                ⁢                  SIR          /          10                    )      
where P(k, i(k)) is a probability of that the number of frame errors during N(k) frames n(k) becomes equal to i(k) (0xe2x89xa6i(k)xe2x89xa6N(k)), and S(k, i(K)) is the increase and decrease value of target SIR when the number of frame errors n(k) is equal to i(k) and when increasing and decreasing are indicated by positive and negative polarities, respectively.
The difference xcex94SIR may be set to a value equal to or higher than xe2x88x922 dB and lower than 0 dB, or a value equal to or lower than 2 dB and higher than 0 dB.
It is preferred that the increase and decrease values of target SIR stored in the table are set to satisfy equation of             ∑              k        =        1            K        ⁢                  ∑                              i            ⁢                          (              k              )                                =          0                          N          ⁢                      (            k            )                              ⁢                        1                      M            ⁢                          (              k              )                                      ⁢                  S          ⁢                      (                          k              ,                              i                ⁢                                  (                  k                  )                                                      )                          xc3x97                  P          ⁢                      (                          k              ,                              i                ⁢                                  (                  k                  )                                                      )                                =  0
where P(k, i(k)) is a probability of that the number of frame errors during N(k) frames n(k) becomes equal to i(k) (0xe2x89xa6i(k)xe2x89xa6N(k)) when a FER is equal to the target FER, and S(k, i(K)) is the increase and decrease value of target SIR when the number of frame errors n(k) is equal to i(k) and when increasing and decreasing are indicated by positive and negative polarities, respectively.
It is also preferred that the increase and decrease values of target SIR stored in the table are set to satisfy equation of                               ∑                      k            =            0                    K                ⁢                              ∑                                          i                ⁡                                  (                  k                  )                                            =              0                                      N              ⁡                              (                k                )                                              ⁢                                    1                              M                ⁡                                  (                  k                  )                                                      ⁢                                          10                ^                                  S                  ⁡                                      (                                          k                      ,                                              i                        ⁡                                                  (                          k                          )                                                                                      )                                                              /              10                                          )        xc3x97          P      ⁡              (                  k          ,                      i            ⁡                          (              k              )                                      )              =  1
where P(k, i(k)) is a probability of that the number of frame errors during N(k) frames n(k) becomes equal to i(k) (0xe2x89xa6i(k)xe2x89xa6N(k)) when a FER is equal to the target FER, and S(k, i(K)) is the increase and decrease value of target SIR when the number of frame errors n(k) is equal to i(k) and when increasing and decreasing are indicated by positive and negative polarities, respectively.
Preferably, the adjusting step is stopped from doing during frames just after the target SIR is once adjusted.
According to the present invention, a control method of transmitting power in a cellular system includes a step of measuring a SIR of a received signal at the receiving side, a step of detecting frame errors of the received signal at the receiving side, a step of counting the number of frames until the number of the detected frame errors becomes m (m is a positive integer) to provide a counted number of frames C each time m frame errors being detected, a step of adjusting a value of a target SIR depending on the counted number of frames C, a step of comparing the measured SIR with the adjusted target SIR to provide a compared result, and a step of controlling at the transmitting side the transmitting power depending on the compared result.
It is preferred that the adjusting step includes comparing the counted number of frames C with thresholds t1 and t2 (t1xe2x89xa6t2), increasing the value of the target SIR by a value S1 when Cxe2x89xa6t1, and decreasing the value of the target SIR by a value S2 when Cxe2x89xa7t2.
It is more preferred that, in case that there is a difference xcex94SIR between the target SIR and a required SIR which satisfies a target FER, the adjusting step further includes setting the values S1 and S2 to satisfy equation of
xe2x80x83S1xc3x97P1xe2x88x92S2xc3x97P2=xcex94SIR
where P1 is a probability of that relationship of the number of frame errors n with respect to the threshold t1 becomes nxe2x89xa7t1, and P2 is a probability of that relationship of the number of frame errors n with respect to the threshold t2 becomes nxe2x89xa6t2.
It is also preferred that, in case that there is a difference xcex94SIR between the target SIR and a required SIR which satisfies a target FER, the adjusting step further includes setting the values S1 and S2 to satisfy equation of
10{circumflex over ( )}(S1/10)xc3x97P1+10{circumflex over ( )}(xe2x88x92S2/10)xc3x97P2+(1xe2x88x92P1xe2x88x92P2)=10{circumflex over ( )}(xcex94SIR/10)
where P1 is a probability of that relationship of the number of frame errors n with respect to the threshold t1 becomes nxe2x89xa7t1, and P2 is a probability of that relationship of the number of frame errors n with respect to the threshold t2 becomes nxe2x89xa6t2.
The difference xcex94SIR may be set to a value equal to or higher than xe2x88x922 dB and lower than 0 dB, or a value equal to or lower than 2 dB and higher than 0 dB.
It is preferred that the adjusting step further includes setting the values S1 and S2 to satisfy equation of
S1xc3x97P1=S2xc3x97P2
where P1 is a probability of that relationship of the counted number of frames C with respect to the threshold t1 becomes Cxe2x89xa6t1 when a FER is equal to the target FER, and P2 is a probability of that relationship of the counted number of frames C with respect to the threshold t2 becomes Cxe2x89xa7t2 when the FER is equal to the target FER.
It is also preferred that the adjusting step further includes setting the values S1 and S2 to satisfy equation of
10{circumflex over ( )}(S1/10)xc3x97P1+10{circumflex over ( )}(xe2x88x92S2/10)xc3x97P2=P1+P2
where P1 is a probability of that relationship of the counted number of frames C with respect to the threshold t1 becomes Cxe2x89xa6t1 when a FER is equal to the target FER, and P2 is a probability of that relationship of the counted number of frames C with respect to the threshold t2 becomes Cxe2x89xa7t2 when the FER is equal to the target FER.
It is preferred that the method further includes preparing a table for storing increase and decrease values of target SIR corresponding to the number of frames C, and that the adjusting step includes obtaining an increase or decrease value from the table depending on a newest number of frames C when it is updated, and increasing or decreasing the value of the target SIR by the obtained value.
It is more preferred that the increase and decrease values of target SIR stored in the table are set to satisfy equation of             ∑              i        =        m            ∞        ⁢                  S        ⁢                  (          i          )                    ⁢              P        ⁢                  (          i          )                      =  0
where P(i) is a probability of that the number of frames C becomes equal to i (mxe2x89xa6i) when a FER is equal to the target FER, and S(i) is the increase and decrease value of target SIR when the number of frames C is equal to i and when increasing and decreasing are indicated by positive and negative polarities, respectively.
According to the present invention, a control method of transmitting power in a cellular system includes a step of measuring a SIR of a received signal at the receiving side, a step of detecting frame errors of the received signal at the receiving side, a step of adjusting a value of a target SIR depending on the detected frame errors, a step of comparing the measured SIR with the target SIR to provide a compared result, a step of controlling at the transmitting side the transmitting power depending on the compared result, a step of judging at the receiving side whether the controlled transmitting power at the transmitting side is at a lower limit level, and a step of prohibiting the adjustment of the value of the target SIR when the judging step judges that the transmitting power is at the lower limit level.
It is preferred that the method further includes a step of sending information indicating that the controlled transmitting power at the transmitting side is at the lower limit level from the transmitting side to the receiving side, and that the judging step includes judging that the controlled transmitting power is at the lower limit level when the information is received at the receiving side.
It is also preferred that the judging step includes monitoring that the measured SIR is higher than the target SIR, and judging that the controlled transmitting power is at the lower limit level when the measured SIR is higher than the target SIR for a predetermined period or more.
According to the present invention, a control method of transmitting power in a cellular system includes a step of measuring a SIR of a received signal at the receiving side, a step of detecting change in the number of connecting cells due to the soft handover or the softer handover, a step of adjusting a value of a target SIR depending on the detected change of the number of the connecting cells, a step of comparing the measured SIR with the target SIR to provide a compared result, and a step of controlling at the transmitting side the transmitting power depending on the compared result.
According to the present invention, a control method of transmitting power in a cellular system includes a step of measuring a SIR of a received signal at the receiving side, a step of detecting change in the number of connecting cells due to the soft handover or the softer handover, a step of adjusting a value of a target SIR depending on the detected change of the number of the connecting cells and on kind of the handovers, a step of comparing the measured SIR with the target SIR to provide a compared result, and a step of controlling at the transmitting side the transmitting power depending on the compared result.
It is preferred that the transmitting side executes control of changing on/off of transmission for every frame, and that the method further includes a step of removing the off-transmission frame from the counted number of frames and also from the counted number of frame errors, and a step of controlling the number of frames N(k) except for the off-transmission frame at constant.
It is also preferred that the transmitting side executes control of changing on/off of transmission for every frame, and that the method further includes a step of removing the off-transmission frame from the counted number of frames and also from the counted number of frame errors, and a step of controlling the number of frame errors m except for the off-transmission frame at constant.
It is preferred that the transmitting side executes control of changing on/off of transmission for every frame, and that the method further includes a step of removing the off-transmission frame from the counted number of frames and also from the counted number of frame errors, and a step of regarding the number of frames except for the off-transmission frame within a period as the number of frames N(k).
It is also preferred that the numbers of frames M(k) and N(k) are time-varying values.
Preferably, the thresholds t1 and t2 are time-varying values.
Also, preferably, the value m is a time-varying value.
It is preferred that the numbers of frames M(k) and N(k), the thresholds t1 and t2, the increase value S1 and the decrease value S2 are informed from the transmitting side to the receiving side.
It is also preferred that the numbers of frames M(k) and N(k) and the increase or decrease value are informed from the transmitting side to the receiving side.
It is preferred that the numbers of frames M(k) and N(k), the thresholds t1 and t2, the increase value S1 and the decrease value S2 are informed from the transmitting side to the receiving side.
It is preferred that the numbers of frames M(k) and N(k) and the increase or decrease value are informed from the transmitting side to the receiving side.
It is preferred that the numbers of frames M(k) and N(k) and the increase or decrease value are informed from the transmitting side to the receiving side.
It is also preferred that the value m, the thresholds t1 and t2, the increase value S1 and the decrease value S2 are informed from the transmitting side to the receiving side.
It is preferred that the value m and the increase or decrease value are informed from the transmitting side to the receiving side.
According to the present invention, a control method of transmitting power in a cellular system includes a step of measuring a power of a received signal at the receiving side, a step of detecting frame errors of the received signal at the receiving side, a step of counting the number of the detected frame errors n(k) (k and n(k) are positive integers and 1xe2x89xa6kxe2x89xa6K) for every M(k) (M(k) is a positive integer) frames, or for last N(k) (N(k) is a positive integer) frames just before the frame error is detected, a step of adjusting a value of a target power depending on one or set of the counted numbers of frame error n(1) to n(K), a step of comparing the measured received signal power with the adjusted target power to provide a compared result, and a step of controlling at the transmitting side the transmitting power depending on the compared result.
It is preferred that, in case of K=1, the adjusting step includes comparing the counted number of frame error n(1) with thresholds t1 and t2 (t1xe2x89xa7t2), increasing the value of the target power by a value S1 when n(1)xe2x89xa7t1, and decreasing the value of the target power by a value S2 when n(1)xe2x89xa6t2.
In this case, preferably, the adjusting step further includes setting the values S1 and S2 to satisfy equation of
S1xc3x97P1=S2xc3x97P2
where P1 is a probability of that relationship of the number of frame errors n(1) with respect to the threshold t1 becomes n(1)xe2x89xa7t1 when a frame error rate is equal to the target frame error rate, and P2 is a probability of that relationship of the number of frame errors n(1) with respect to the threshold t2 becomes n(1)xe2x89xa6t2 when the frame error rate is equal to the target frame error rate.
It is also preferred that the method further includes preparing a table for storing increase and decrease values of target power corresponding to the number of frame errors n(1), and that, in case of K=1, the adjusting step includes obtaining an increase or decrease value from the table depending on a newest number of frame error n(1) when it is updated, and increasing or decreasing the value of the target power by the obtained value.
In this case, preferably, the increase and decrease values of target power stored in the table are set to satisfy equation of             ∑              i        =        0            N        ⁢                  S        ⁢                  (          i          )                    ⁢              P        ⁢                  (          i          )                      =  0
where P(i) is a probability of that the number of frame errors n(1) becomes equal to i (0xe2x89xa6ixe2x89xa6N =N(1)) when a frame error rate is equal to the target frame error rate, and S(i) is the increase and decrease value of the target power when the of frame errors n(1) is equal to i (0xe2x89xa6ixe2x89xa6N=N(1)) and when increasing and decreasing are indicated by positive and negative polarities.